Radioactive iodine uptake in hyperthyroid cats after administration of recombinant human thyroid stimulating hormone.

BACKGROUND: Radioactive iodine therapy is considered the treatment of choice for hyperthyroidism in cats, but the availability of this modality is limited by costs and hospitalization requirements. Administration of recombinant human thyroid stimulating hormone (rh-TSH) to humans with thyroid neoplasia or nodular goiter can increase thyroidal iodine uptake, thereby allowing the use of lower radioactive iodine doses for treatment. Veterinary studies of this subject are limited, and results are conflicting. OBJECTIVE: To investigate the effects of rh-TSH administration on thyroidal iodine uptake in hyperthyroid cats. ANIMALS: Ten client-owned hyperthyroid cats. METHODS: In this prospective clinical study, cats were administered saline (placebo), 50 µg rh-TSH (low-dose), and 100 µg rh-TSH (high-dose) in randomized crossover design with treatments separated by 7-10 days. After each treatment, thyroid scintigraphy was performed by administering 300 µCi 123 I and assessing radionuclide uptake 8 and 24 hours later. Serum thyroid hormone concentrations were measured at each visit. RESULTS: Thyroidal percent iodine uptakes (mean ± SD at 8 and 24 hours) in cats treated with placebo (25.2 ± 13.4%, 30.0 ± 12.8%), low-dose (24.1 ± 12.5%, 29.4 ± 13.7%), and high-dose rh-TSH (24.2 ± 16.3%, 30.8 ± 15.3%) were not different (P = .76). Independent of rh-TSH administration, percent iodine uptakes were positively correlated with serum thyroid hormone concentrations. CONCLUSIONS AND CLINICAL IMPORTANCE: One-time administration of rh-TSH, even at high doses, would not be expected to lower radioactive iodine doses needed for treatment of hyperthyroidism in cats. Investigations of alternate strategies to increase thyroidal uptake of radioactive iodine are warranted.

Evaluation of a modified infraorbital approach for a maxillary nerve block for rhinoscopy with nasal biopsy of dogs.

OBJECTIVE To determine whether a maxillary nerve block via a modified infraorbital approach, applied before rhinoscopy and nasal biopsy of dogs, would decrease procedural nociception, minimize cardiorespiratory anesthetic effects, and improve recovery quality. ANIMALS 8 healthy adult hound-type dogs PROCEDURES In a crossover study, dogs received 0.5% bupivacaine (0.1 mL/kg) or an equivalent volume of saline (0.9% NaCl) solution as a maxillary nerve block via a modified infraorbital approach. A 5-cm, 20-gauge over-the-needle catheter was placed retrograde within each infraorbital canal, and bupivacaine or saline solution was administered into each pterygopalatine region. Rhinoscopy and nasal biopsy were performed. Variables monitored included heart rate, systolic arterial blood pressure (SAP), mean arterial blood pressure (MAP), diastolic arterial blood pressure (DAP), plasma cortisol and norepinephrine concentrations, purposeful movement, and pain scores. After a 14-day washout period, the other treatment was administered on the contralateral side, and rhinoscopy and nasal biopsy were repeated. RESULTS SAP, MAP, and DAP were significantly higher for the saline solution treatment than for the bupivacaine treatment, irrespective of the time point. Plasma cortisol concentrations after saline solution treatment were significantly higher 5 minutes after nasal biopsy than at biopsy. Heart rate, norepinephrine concentration, purposeful movement, and pain score were not significantly different between treatments. CONCLUSIONS AND CLINICAL RELEVANCE Maxillary nerve block via a modified infraorbital approach prior to rhinoscopy and nasal biopsy reduced procedural nociception as determined on the basis of blood pressures and plasma cortisol concentrations during anesthesia. These findings warrant further evaluation in dogs with nasal disease.

Comparison of Morphine, Morphine-Lidocaine, and Morphine-Lidocaine-Ketamine Infusions in Dogs Using an Incision-Induced Pain Model.

We aimed to compare antinociceptive effects of IV infusions of morphine (M), morphine-lidocaine (ML), or morphine-lidocaine-ketamine (MLK) combined, in a mild-to-moderate pain model in dogs. Eighteen adult hounds were heavily sedated with IV morphine (0.2 mg/kg) and dexmedetomidine to undergo thoracic skin incisions. After reversal, dogs were randomly assigned to receive loading doses of lidocaine and ketamine (MLK), lidocaine and saline (ML), or equivalent volume of saline (M), followed by 18 hr constant infusions of morphine (0.12 mg/kg/hr), lidocaine (3 mg/kg/hr) and ketamine (0.6 mg/kg/hr); morphine (0.12 mg/kg/hr) and lidocaine (3 mg/kg/hr); or morphine (0.12 mg/kg/hr), respectively. Pain was assessed with Short Form Glasgow Composite Measure Pain Scale and mechanical nociception with von Frey filaments (VFFS). Data were analyzed with linear mixed model on ranks. Independently of treatment, Short Form Glasgow Composite Measure Pain Scale was significantly higher than baseline for 24 hr (p < .0001), while VFFS was significantly lower than baseline for 48 hr post-recovery (p < .0001), with no difference between MLK and M groups. The ML group recorded significantly lower VFFS (p = .02) than the M group for the entire study. In conclusion, there was no significant analgesic difference between MLK and M alone.

Anticoagulant effects of inhaled unfractionated heparin in the dog as determined by partial thromboplastin time and factor Xa activity.

OBJECTIVE: To evaluate the anticoagulant effects of inhaled heparin in dogs. DESIGN: This study was conducted in 3 phases. In phase 1, bronchoalveolar lavage fluid (BALf) was collected to generate an in vitro calibration curve to relate heparin concentration to the activated partial thromboplastin time (aPTT). In phase 2, heparin was administered via nebulization to determine the threshold dose needed to prolong systemic aPTT. In phase 3, the local anticoagulant activity of inhaled heparin was determined by measurement of BALf anti-Xa activity and aPTT. SETTING: University teaching hospital. ANIMALS: Six healthy intact female Walker Hounds were used in this study. Two dogs were used for each phase. INTERVENTIONS: Inhaled unfractionated sodium heparin was administered in doses ranging from 50,000 to 200,000 IU. RESULTS: In vitro addition of heparin to BALf caused a prolongation in aPTT. Inhaled heparin at doses as high as 200,000 IU failed to prolong systemic aPTT, and a threshold dose could not be determined. No significant local anticoagulant effects were detected. CONCLUSIONS: Even at doses higher than those known to be effective in people, inhaled heparin appears to have no detectable local or systemic anticoagulant effects in dogs with the current delivery method.

Quantification and comparison of baseline cortisol levels between aqueous and plasma from healthy anesthetized hound dogs utilizing mass spectrometry.

OBJECTIVE: The purpose of this study is to quantify and compare the resting cortisol levels between aqueous (Aq) and plasma of anesthetized hound dogs utilizing mass spectrometry. ANIMALS: Nine hound breed dogs weighing between 20.8 and 29.2 kg (x = 26.3 kg, SD ± 2.6 kg) were utilized from a previous project. PROCEDURES: All dogs underwent two anesthesia sessions to harvest Aq from each eye respectively. A paired blood sample was taken immediately after aqueous centesis. The Aq and plasma were analyzed for cortisol levels using mass spectrometry. Correlation of cortisol levels in dog serum and ocular fluid was determined with Sigma Stat using Pearson's correlation analysis. The level of significance for correlation analysis was set at P < 0.05. RESULTS: The plasma resting cortisol levels in the dog ranged from 3.59 to 89.35 nm (x = 31.68 nm, SD ± 28.53 nm), while the Aq cortisol levels ranged from 0.82 to 5.62 nm (x = 2.73 nm, SD ± 1.94 nm). The correlation of cortisol levels in Aq compared to plasma was significant (P = 0.008) with a correlation coefficient of r = 0.779. Based on these results, 61% (r = 0.779(2) ) of the variation in Aq cortisol levels is explained by the variations in plasma cortisol levels. CONCLUSION AND CLINICAL RELEVANCE: This study identified significant levels of cortisol in the Aq of the canine eye and positively correlated them with plasma cortisol levels. The dog may offer a representative model for further studies to help clarify the overall role of cortisol in the anterior chamber.

Electrocardiography-guided and retrospective analysis of central venous catheter placement in the dog.

OBJECTIVE: To compare the success rates of central venous catheter placement (CVCP) in dogs using electrocardiograph (ECG)-guided and external landmark ('blind') techniques. To report success rates determined retrospectively of CVCPs in dogs using external landmarks at a tertiary referral institution. STUDY DESIGN: Prospective blinded comparison of techniques. Retrospective analysis of case records. ANIMALS: Adult Beagles weighing 11.9 +/- 2.6 kg were used in the experimental group (n = 38). Various breeds of dogs were in the retrospective clinical group (n = 33). METHODS: Laboratory dogs were anesthetized and CVCPs were placed using a modified Seldinger technique. Catheter tip position was first based on external landmarks and then the catheter was repositioned using an ECG-guided placement. The ECG-guided technique used the V-lead with the positive electrode attached to the guide wire. Catheter placement was determined by moving the catheter cephalad and caudad to the point of maximum p-wave amplitude and then withdrawing the catheter 1-2 cm from this point. Catheter position with each technique was determined using a lateral thoracic radiograph. Retrospective data were collected from the medical records of dogs that had CVCPs using anatomical landmarks and corresponding thoracic radiographs. RESULTS: The number of successful CVCP attempts was the same for both prospective groups (21/38). There was no statistically significant difference in success between the ECG-guided technique and the blind technique. From the retrospective investigation 10/33 of the cases that fit the criteria had correct CVCPs. CONCLUSIONS AND CLINICAL RELEVANCE: The odds of correctly placing a central venous catheter by ECG-guidance were the same as the external landmark technique. The ECG-guided technique may be useful in situations where external landmarks are not readily available.